Generally, a motor is an apparatus which changes electric energy into kinetic energy, and it is classified into a rotating type motor which changes the electric energy into rotational motion and a reciprocating motor which changes the electric energy into linear reciprocating motion.
The motor is used in many ways as a power source. Especially, it is installed in almost electric appliances such as refrigerator, air conditioner, washing machine, and electric fan, etc. In case of refrigerator and air conditioner, it is able to be used to rotate a blast fan, but also used as a power source by being installed on a compressor in a refrigerating cycle device constituting the refrigerator and the air conditioner.
FIG. 1 shows an embodiment of a conventional reciprocating motor. As shown therein, the reciprocating motor comprises a stator (S) includes a cylindrical outer core 10 and an inner core 20 inserted with a certain gap from the outer core 10; a winding coil 30 coupled to the outer core 10 or to the inner core 20; and an armature 40 inserted between the outer core 10 and the inner core 20 so as to be capable of performing linear reciprocating movement.
FIG. 1 shows the structure that the winding coil 30 is coupled to the outer core 10.
The outer core 10 is formed as a cylindrical laminated body by stacking radially a plurality of lamination sheets 11 formed as “U”-shaped thin plates having a certain width so as to make a cylinder shape.
The “U”-shaped part of the lamination sheet 11 is a pass unit 11a on which a flux flows, both ends of the lamination sheet 11 are pole units 11b forming the poles, and an opened space formed inside the pass unit 11a is an opened unit 11c on which the winding coil 30 is located.
The winding coil 30 is formed so that the shape of its profile is corresponded with that of the opened unit 11c by winding the coil a plurality of times so as to make an annular shape. On outer circumference surface of the winding coil 30, an insulation coating film 31 is formed.
The inner core 20 is formed as a cylindrical laminated body by radially stacking the lamination sheet 21 formed as a square thin plate having a same length as that of the outer core 10.
The armature 40 includes a cylindrical magnet holder 41 inserted between the outer core 10 and the inner core 20, and a plurality of permanent magnets 42 fixedly coupled to the outer surface of the magnet holder 41.
The winding coil 30 and the outer core 10 is coupled as follows, that is, the insulation coating film 31 is coated on outer side of the winding coils 30 wound a coil a plurality of times so as to make an annular form, and in that state, the lamination sheet 11 constructing the outer core 10 coupled to the winding coil by being stacked radially on the winding coil 30.
At that time, the lamination sheet 11 is stacked on the winding coil 30 so that the winding coil 30 is inserted inside the opened unit 11c. 
The length of the permanent magnets 42 (Lm) is usually same as the length of the pole unit (Lp) added with the length between the poles (Lb). Therefore, the length of the permanent magnets 42 is in proportion to the length between the poles located on both ends of the opened unit 11c, that is, the length between the poles (Lb), therefore the shorter the length between the poles (Lb), the shorter the length of the permanent magnets 42 (Lm). The length of the pole unit (Lp) is corresponded to the stroke, and the length between the poles (Lb) is corresponded to the width of entrance of the opened unit 11c. 
As shown in FIG. 2, the reciprocating motor described above is operated as follows. First, if the electric current flows on the winding coils 30, a flux is formed around the winding coils 30 by the current flowing on the coils. And the flux flows along with the pass unit 11a of the outer core and the inner core 20 forming the stator (S) as forming a closed loop.
The permanent magnets 42 are moved to the axial direction by the interaction between the flux formed by the electric current flowing on the winding coil 30 and the flux formed by the permanent magnets 42 constituting the armature 40.
In addition, if the flowing direction of the electric current on the winding coil 30 is changed, the direction of the flux formed on the pass unit 11a of the outer core and on the inner core 20 is changed, and the permanent magnets 42 are moved to the opposite direction.
Like above, if the electric current is supplied as changing the direction, the permanent magnets 42 undergoes linear reciprocating motion between the outer core 10 and the inner core 20. Accordingly, the armature 40 generates the driving force of the linear reciprocating motion.
However, in the structure described above, the outer core 10 is constructed as a plurality of lamination sheets 11 is stacked by manual work on the winding coil 30, in the state that insulation coated on the winding coil 30 made by winding a coil having a certain length a plurality of times. Therefore, the winding coil 30 having a same shape as that of the opened unit 11c of the lamination sheet constructing the outer core 10 is difficult to make.
In addition, the winding coil 30 is easy to be distorted, so it becomes difficult to stack the lamination sheet 11, and its size is not to be precise. Therefore, the gap between the outer core 10 and the inner core 20 in which the armature is inserted is not capable of being maintained precisely, whereby the armature 40 is contacted between the outer core and the inner core, and the armature is worn.
Moreover, the width of the entrance of the opened unit 11c on which the winding coil 30 is located, that is, the length between the poles (Lb) is long, and therefore the length of the permanent magnet 42 of high price which is dependant on that of between the poles (Lb), and the amount of the permanent magnet 42 is increased. Thereby, the production cost is increased, and the manufacturing period and the process becomes longer because the lamination sheet 11 is stacked by manual work, so it is not suitable for mass product.